Each call leg at a particular UA is defined by the To, From and Call-ID.
The To header should be different for the Invite to the new leg for the
transfer, so the same Call-ID could be used.
-----Original Message-----
From: Paul D.Smith [mailto:[EMAIL PROTECTED]]
Sent: Monday, July 16, 2001 9:36 AM
To: '[EMAIL PROTECTED]'
Subject: [Sip-implementors] REFER and use of Call-ID
I'm sure this has been worked over before but can someone please shed some
light on the following apparent disconnect regarding Call-ID: between the
"SIP Call Control - Transfer" specification and the base SIP specification?
The base SIP specification says the following about Call-ID.
--- From RFC 2543 ---
6.12 Call-ID
The Call-ID general-header field uniquely identifies a particular invitation
or all registrations of a particular client. Note that a single multimedia
conference can give rise to several calls with different Call-IDs, e.g., if
a user invites a single individual several times to the same (long-running)
conference.
---
This implies that each INVITE (not RE-INVITEs) results in a new Call-ID.
Compare this to the REFER specification, draft-ietf-sip-cc-transfer-04,
where the Refer-to: header can take the following value:
--- From ...transfer-04 ---
Refer-To:
sip:[EMAIL PROTECTED]?Accept-Contact=sip:bobsdesk.biloxi.com&Call-ID=55432@alic
epc.atlanta.com
----
The REFER specification goes on to give examples (4.5.1 and 4.7) of calls
being transferred by issuing new INVITEs, to new partners, using the _same_
Call-ID as the original call which is being transferred.
So my question is how can the two specifications be consistent? It appears
to me that RFC 2543 requires each new INVITE to use a new Call-ID whereas
...transfer-04 allows a new INVITE to reuse an existing Call-ID. What is
the consensus on which interpretation is correct or most widely used?
Thanks in advance for your clarifications,
Paul D.Smith.
> Paul D.Smith
> Voice Networking Group
> Data Connection Ltd
> Tel: +44 20 8366 1177
> Fax: +44 20 8367 8501
> Email: [EMAIL PROTECTED]
> Web: http://www.dataconnection.com
>
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